// Creates a redo unit from an undo unit.
private CompositionParentUndoUnit(CompositionParentUndoUnit undoUnit)
: base(undoUnit)
{
_isFirstCompositionUnit = undoUnit._isFirstCompositionUnit;
_isLastCompositionUnit = undoUnit._isLastCompositionUnit;
}
// Merges another unit into this unit.
internal void MergeCompositionUnit(CompositionParentUndoUnit unit)
{
object[] units = unit.CopyUnits();
Invariant.Assert(this.Locked); // If this fails, then the Locked = true below is invalid.
this.Locked = false;
for (int i = units.Length - 1; i >= 0; i--)
{
Add((IUndoUnit)units[i]);
}
this.Locked = true;
MergeRedoSelectionState(unit);
_isLastCompositionUnit |= unit.IsLastCompositionUnit;
}
// Opens the composition undo unit if it exists on the top
// of the stack. Otherwise, create a new composition undo unit
// and add it to the undo stack.
private CompositionParentUndoUnit OpenCompositionUndoUnit(ITextPointer compositionStart, ITextPointer compositionEnd)
{
UndoManager undoManager = UndoManager.GetUndoManager(this.TextContainer.Parent);
if (undoManager == null || !undoManager.IsEnabled)
{
return null;
}
// The start position is where we'll put the caret if this composition is later
// undone by a user.
//
// At this point some IMEs will not have updated the selection to a
// position within the composition, suggesting that we always want to
// use selection start. However, some IMEs will expand the composition backward on input
// so the composition covers unmodified text. (E.g.: chinese prc pinyin IME
// will expand to cover previously finalized text on <space> input.)
//
// So we use a hueristic: take the rightmost of the selection start or composition
// start.
ITextPointer start;
if (compositionStart == null)
{
Invariant.Assert(compositionEnd == null);
GetCompositionPositions(out compositionStart, out compositionEnd);
}
if (compositionStart != null && compositionStart.CompareTo(this.TextSelection.Start) > 0)
{
start = compositionStart;
}
else
{
start = this.TextSelection.Start;
}
CompositionParentUndoUnit unit = new CompositionParentUndoUnit(this.TextSelection, start, start, _nextUndoUnitIsFirstCompositionUnit);
_nextUndoUnitIsFirstCompositionUnit = false;
// Add the given composition undo unit to the undo manager and making it
// as the opened undo unit.
undoManager.Open(unit);
return unit;
}
